This invention relates to a two-way differential clutch using sprags.
In part-time four-wheel drive vehicles, an overrunning type two-way differential clutch is used to automatically transmit the driving force to the front vehicle wheels as soon as a rear wheel slips and the vehicle speed drops.
In unexamined Japanese patent publication 9-25959, an overrunning type two-way differential clutch using sprags is disclosed. It includes two retainers having different diameters and mounted between the outer circumferential surface of a rotary shaft and the inner circumferential surface of an input gear mounted on the rotary shaft. The large-diameter retainer is fixed to the input gear while the small-diameter one is rotatably supported on the rotary shaft so as to create a differential speed between the small-diameter retainer and the large-diameter retainer, which rotates together with the input gear, due to a frictional resistance applied to the small-diameter retainer so that sprags mounted to straddle pockets formed in both of the retainers will be inclined or tilted to a standby state in which they contact at both ends thereof the outer circumferential surface of the rotary shaft and the inner circumferential surface of the input gear. Thus, when the rotating speed of the rotary shaft drops below that of the input gear, the sprags are brought into an engaging state to transmit the rotation of the input gear to the rotary shaft.
With such a two-way differential clutch, when the rotating direction of the input gear changes over, the inclining direction of the sprags also changes automatically. Thus it is possible to transmit the rotation of the input gear in either direction to the rotary shaft.
In many cases, as a means for giving a rotational resistance to the small-diameter retainer, an arrangement is employed in which a flange is provided on the outer surface of the small-diameter retainer at its end protruding beyond one end of the input gear, a friction plate provided on one side of the flange being supported so as to be movable in the axial direction of the small-diameter retainer, and the friction plate being pressed against the flange by a partially cut-apart resilient ring supported on the small-diameter retainer.
In this two-way differential clutch, if such a resilient ring is used as a resistance-imparting means for imparting a frictional resistance to the small-diameter retainer, it may expand radially outwardly during high-speed rotation, thus coming off its position. In such a case, a frictional force between the friction plate and the flange will disappear, so that the small-diameter retainer becomes freely rotatable. The two-way differential clutch thus becomes inoperative to exhibit its function as a clutch. #
Also, for such a two-way differential clutch, since the input gear and the small-diameter retainer are rotatably supported by respective rolling bearings mounted on the rotary shaft and both ends of the rotary shaft are rotatably supported by two rolling bearings, when the clutch is assembled, an assembling step in which four rolling bearings are pressed is needed, so that it takes a long time to assemble. Thus, there is room for improvement in assembling it.
Also, after pressing, the rolling bearings need setting of clearance. At this time, since the clearance setting range is wide due to variations in e.g. tolerances of the parts at the press-in portion, it is difficult to obtain high-precision assembling. Thus, improvement in the assembling accuracy is required.
An object of this invention is to provide a two-way differential clutch which can prevent the resilient ring for biasing the friction plate from expanding radially outwardly and getting off the mounting position due to centrifugal force during high-speed rotation.
A second object of this invention is to improve assembling properties and assembling accuracy of a two-way differential clutch.